On this protocol we will see patients of all ages with a neurodegenerative disorder of unknown etiology, as well patients with known diseases that are atypical or present difficult management problems. Patients with a known or a suspected leukodystrophy will be excluded from this study. Lack of specific diagnosis amplifies the distress felt by patients and families and decreases the chance of effective therapy. Clinical and laboratory evaluation will include blood, urine, spinal fluid, peripheral tissue pathology and radiological studies.